The present invention relates to a self-light-emitting apparatus, such as for example, an organic or inorganic electroluminescence (EL) display device and the like and a semiconductor device, such as a thin film transistor (TFT) used in the apparatus.
In an organic EL display device, many of organic EL elements are arranged in matrix on a substrate. Each of the EL elements, namely a pixel (picture element), consists of a transparent electrode layer, an organic EL layer and an upper electrode layer. At least one thin film transistor for controlling current applied to the EL element is electrically connected to this EL element.
In such an active matrix type organic EL display device, a connecting line from an X-direction peripheral drive circuit, a connecting line from a Y-direction peripheral drive circuit and a connecting line from a power supply (Vdd) are certainly intersected to each other. Thus, the intersected portions of these connecting lines should have a multi-layered structure of two or more layers through insulation interlayer(s) so that they are not short-circuited to each other.
In this multi-layered structure, a connecting line (a lower layer line) which is a lower side layer is connected to a silicon active layer or gate electrode silicon layer of a thin film transistor at the lower surface thereof, and is connected to an upper side electrode line or a transparent electrode of a EL pixel at the upper surface thereof.
Therefore, in addition to a low electric resistance, a material of the lower layer line should have a function as a barrier metal to prevent the diffusion of silicon into an aluminum line, and a function that the material is not damaged during etching of a insulation interlayer to form a contact hole, namely a chemical resistance which is not etched by ammonium fluoride during wet etching and a sufficient selection ratio (ratio of the etching rates) for the insulation interlayer during an dry etching. Further, the material of the lower layer line should also be able to perform an electrically stable connection to the upper side electrode line.
It is also required that the material of the lower layer line does not generate a hillock by thermal stress applied during depositing the insulation interlayer, that is a projected portion of the material is not formed by being crystallized. Additionally, the material should also be able to perform an electrically stable connection to a transparent electrode made of a material such as ITO (Indium Tin Oxide) or the like which is apt to react with other materials.
In a TFT for an organic EL display device, which the present inventor et al of the present application developed, although not forming a prior art for the present invention, titanium nitride containing equal to or less than 50 atm % of nitrogen is used as a material with these functions (U.S. Pat. No. 5,640,067).
Titanium nitride has a relatively large resistance (Specific resistance is equal to or more than 90 xcexcxcexa9xc2x7cm, and sheet resistance is equal to or more than 5 xcexa9/xe2x96xa1). Thus, titanium nitride is used as a material of the lower layer line of an organic EL display device, it is necessary for the film thickness to be for example 2500 Angstroms or more to lower the resistance value.
Further, it is very difficult to work titanium nitride. Thus, when a thick titanium nitride film is worked by dry etching, the working time is long and damage to portions other than titanium nitride is increased, and further short-circuit easily occurs due to a remaining titanium nitride film on a stepped sidewall portion. This often results in electrical defects.
Alternatively, when the thick titanium nitride film is worked by wet etching, problems of damage due to the etching and of the remaining titanium nitride film on the stepped side wall portion do not occur. Nevertheless, it was impossible to obtain miniaturization and high resolution of an organic EL display apparatus with a specification better than currently being used.
As mentioned above, when titanium nitride is used, it was impossible to obtain miniaturization and high resolution of an organic EL display device with a specification better than currently being used.
Therefore it is an object of the present invention to provide a self-light-emitting apparatus which is capable of further obtaining miniaturization and high resolution of a self-light-emitting apparatus, such as an organic or inorganic EL display device and the like, and a semiconductor device used in the apparatus.
It is another object of the present invention to provide a self-light-emitting apparatus using a line material in which a high reliability can be obtained.
According to the present invention, there is provided a semiconductor device formed in a self-light-emitting apparatus having a substrate and a plurality of self-light-emitting elements formed on the substrate, the semiconductor device being used to drive one of the self-light-emitting elements. This semiconductor device includes an active layer of a semiconductor material, in which a source region and a drain region are formed, a source electrode having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance, the source electrode electrically being coupled to the source region, a drain electrode having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance, the source electrode electrically being coupled to the drain region, an insulation layer formed on the active layer, and a gate electrode formed on the insulation layer.
Thus, in the present invention, a source electrode and a drain electrode which are connected to an active layer of a semiconductor device, such as a thin film transistor, is formed-of a barrier metal layer having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance. Such a barrier metal layer having a multi-layered structure has heat resistance and chemical resistance and further a stable property.
Further, the barrier metal of the present invention can more extremely reduce the specific resistance in comparison with a titanium nitride single layer. Therefore, in the present invention, essential functions of a barrier metal can be obtained, and further the connecting line can be miniaturized.
It is preferred that the high melting point metal having low resistance is a metal having specific resistance equal to or more than 10-30 xcexcxcexa9xc2x7cm and a melting point equal to or more than 800xc2x0 C.
It is further preferred that the high melting point metal having low resistance is one metallic material selected from groups of tungsten, molybdenum, tantalum, titanium and nickel.
It is also preferred that the self-light-emitting apparatus is an organic or inorganic electroluminescence display device.
Further, according to the present invention, there is also provided a self-light-emitting apparatus having a substrate, a plurality of self-light-emitting elements formed on the substrate and a plurality of semiconductor devices formed on the substrate, the semiconductor devices being connected to respective the self-light-emitting elements for controlling current applied to the plurality of self-light-emitting elements.
This semiconductor device includes: an active layer of semiconductor material, in which a source region and a drain region are formed, a source electrode having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance, the source electrode electrically being coupled to the source region, a drain electrode having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance, the source electrode electrically being coupled to the drain region, an insulation layer formed on the active layer, and a gate electrode formed on the insulation layer. The self-light-emitting apparatus further includes a connecting conductor having a multi-layered structure including an upper side layer of titanium nitride for connecting each of the semiconductor devices to each of the self-light-emitting elements.
It is preferred that the high melting metal having low resistance is a metal having specific resistance equal to or more than 10-30 xcexcxcexa9xc2x7cm and a melting point equal to or more than 800xc2x0 C. It is further preferred that the high melting point metal having low resistance is one metallic material selected from groups of tungsten, molybdenum, tantalum, titanium and nickel.
It is also preferred that the self-light-emitting apparatus is an organic or inorganic electroluminescence display device. In this case, it is further preferred that each of the self-light-emitting elements is an organic or inorganic electroluminescence element having a transparent electrode, and the connecting conductor having a multi-layered structure is connected to the transparent electrode.
Thus, since in order to connect the semiconductor device to the transparent electrode of the EL element, a connecting conductor having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance, the connection to the electrode, which is likely to generate electric corrosion during etching and to generate contact failure due to oxidative effect, can stably be carried out.
Further, according to the present invention, there is provided an active matrix driving type self-light-emitting apparatus having a substrate, a plurality of self-light-emitting elements formed on the substrate and a plurality of semiconductor devices formed on the substrate, the semiconductor devices being connected to respective the self-light-emitting elements for controlling current applied to the plurality of self-light-emitting elements.
This self-light-emitting apparatus includes an insulation interlayer, and an upper side conductor layer and a lower side conductor layer intersecting to each other through the insulation interlayer, the upper side conductor layer being formed of aluminum material, and the lower side conductor layer being a conductor layer having a multi-layered structure including an upper side layer of titanium nitride and a lower side layer of a high melting point metal having low resistance.
It is preferred that the high melting metal having low resistance is a metal having specific resistance equal to or more than 10-30 xcexcxcexa9xc2x7cm and a melting point equal to or more than 800xc2x0 C. Further, the high melting point metal having low resistance is one metallic material selected from groups of tungsten, molybdenum, tantalum titanium and nickel.
It is also preferred that the self-light-emitting apparatus is an organic or inorganic electroluminescence display device.
Further objects and advantages of the present invention will be apparent from description of the preferred embodiments of the invention as illustrated in the accompanying drawings.